/cc @kubernetes/rh-cluster-infra

cc/ @taotaotheripper

Lantao, I am assigning this to you.

cc/ @yifan-gu on RKT support side.

sgtm. FWIW, appc has similar concept called annotations Once we have apis to read them from rkt, we don't have to store everything in service files.

I just put restart count into docker label last week in #15965.
Next step, I'll try to move pod name and namespace into docker label, and use label filter to simplify GetPodStatus().
Just update my progress here, :)

@Random-Liu: Thanks for working on this! Looking forward to those patches.

@vishh Thank you, I'll keep working! :)

I put pod full name into docker label and add label filter in GetPodStatus() in #16414.
Again, just update my progress, :)

Progress Update
Currently, we can only add labels to newly created containers, but for containers started already, we can do nothing. So we can't do filter list or naming cleanup etc. which must ensure that all containers' labels have been set properly.

At least till now, the best solution is to add labels on running containers, but docker doesn't support that yet. I submitted an issue in docker community moby/moby#17457. And there is also related discussion moby/moby#15496. Hope that docker will add this feature soon.

Anyhow, for the next step, I'll keep on moving all the other related things into docker label. :)

To figure out whether docker list with label filter could improve the efficiency, I did a simple experiment.

Benchmark
Call client.ListContainers() of go-dockerclient 100 Times.

• Total Container Number: 6101
• Container Number (with label "test=1"): 100
• Container Number (with label "single=1"): 1
• Code (Really Simple)

Result

• ListContainers()
  • each call time: 260.82 (ms)
  • total cpu time: 6.17 (s)
  • total time: 26.08 (s)
  • cpu profile
• ListContainers() with filter "test=1"
  • each call time: 179.72 (ms)
  • total cpu time: 0.22 (s)
  • total time: 17.97 (s)
  • cpu profile
• ListContainers() with filter "single=1"
  • each call time: 174.09 (ms)
  • total cpu time: 0.02 (s)
  • total time: 17.41 (s)
  • cpu profile

Related Code in Docker
api/server/router/local/local.go=>api/server/router/local/container.go#getContainerJSON() =>daemon/list.go#Containers()
Just list all the containers, then do filter.

Conclusion

• On the docker client side, the main overhead is JSON decoding now. Using filter can reduce some of the cost.
• At least till now, docker haven't done indexing for filtering, just list and filter.

At least till now, docker haven't done indexing for filtering, just list and filter.

I guess this was what we were assuming is true with labels. Is there an issue filed against docker to improve label based queries?

@vishh In the original proposal of docker label, they proposed indexing and performance. I just check the code to figure out whether they have done that, :)

As originally proposed, I think we should write TerminationMessagePath as a docker label, so that we don't need to rely on the pod spec to examine a terminated container.

OK. I'll do it. :)

Progress Update
The issue moby/moby#15496 about mutable container label attracted some attention these days, and "status/needs-attention" label has been added to it. Hope we'll have mutable container label soon, :)

Progress Update
Docker has started working on mutable label see here
And the original issue moby/moby#15496 has been marked as status/claimed.

I believe we can close this one too. @Random-Liu, thanks for working on it!

@yujuhong Yeah. Maybe after moby/moby#18958 is landed, we can do something more. For now, I think we have done most of the things. :)